1978694491 has 2 divisors, whose sum is σ = 1978694492. Its totient is φ = 1978694490.

The previous prime is 1978694467. The next prime is 1978694507. The reversal of 1978694491 is 1944968791.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1978694491 - 2²¹ = 1976597339 is a prime.

It is not a weakly prime, because it can be changed into another prime (1978692491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 989347245 + 989347246.

It is an arithmetic number, because the mean of its divisors is an integer number (989347246).

Almost surely, 2^1978694491 is an apocalyptic number.

1978694491 is a deficient number, since it is larger than the sum of its proper divisors (1).

1978694491 is an equidigital number, since it uses as much as digits as its factorization.

1978694491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3919104, while the sum is 58.

The square root of 1978694491 is about 44482.5189372185. The cubic root of 1978694491 is about 1255.4311922891.

The spelling of 1978694491 in words is "one billion, nine hundred seventy-eight million, six hundred ninety-four thousand, four hundred ninety-one".